Hybrid low dew point compressed air dryer

Abstract

The present disclosure is directed to a dryer system for drying compressed gas discharged from a compressor. The dryer system includes a refrigeration drying system operable for removing moisture from the compressed gas and a desiccant drying system with a desiccant wheel located in series downstream of the refrigeration drying system operable for removing additional moisture from the compressed gas.

What is claimed is: 
     
       1. A system comprising:
 a fluid compressor operable to compress a working fluid; 
 a dryer system in fluid communication with the compressor, the dryer system comprising:
 a refrigeration drying system operable for removing moisture from the working fluid; and 
 a desiccant drying system located downstream of the refrigeration drying system, the desiccant drying system operable for removing additional moisture from the working fluid; 
 wherein the working fluid upstream of the desiccant drying system is split into a first flow stream and a second flow stream. 
 
 
     
     
       2. The system of  claim 1 , wherein the desiccant drying system includes a desiccant wheel. 
     
     
       3. The system of  claim 2 , wherein the working fluid downstream of the refrigeration drying system is split into a first flow stream and a second flow stream. 
     
     
       4. The system of  claim 3 , wherein additional moisture is removed from the first flow stream in the desiccant wheel. 
     
     
       5. The system of  claim 3 , wherein the second flow stream regenerates the desiccant wheel after being heated by hot discharge gas from a refrigeration compressor. 
     
     
       6. The system of  claim 3 , wherein a pressure dew point temperature of the first flow stream is subfreezing and an actual temperature of the first flow stream is above freezing downstream of the desiccant wheel. 
     
     
       7. The system of  claim 6 , wherein the pressure dew point temperature is approximately negative 10 degrees F. and the actual temperature is approximately 40 degrees F. 
     
     
       8. The system of  claim 3 , wherein a mass flow rate of the first flow stream is approximately eighty percent of a combined mass flow rate of the first and second flow streams. 
     
     
       9. The system of  claim 3 , wherein the second flow stream merges with the working fluid compressed by the fluid compressor between a precooler and a refrigerant evaporator after exiting the desiccant wheel. 
     
     
       10. The system of  claim 3 , wherein the first flow stream flows through a preheater downstream of the desiccant wheel. 
     
     
       11. A gas dryer comprising:
 a primary gas flow path extending through a refrigerant dryer circuit and subsequently through a desiccant dryer circuit; 
 a secondary gas flow path split off from the primary gas flow path upstream of the desiccant dryer circuit; 
 a moisture separator positioned in the refrigerant dryer circuit configured to remove moisture from a gas in the primary gas flow path; 
 a desiccant wheel positioned in the desiccant dryer circuit configured to remove additional moisture from the gas in the primary gas flow path; and 
 a regeneration flow path extending through the desiccant wheel, the regeneration flow path in fluid communication with the secondary gas flow path. 
 
     
     
       12. The gas dryer of  claim 11  further comprising a coalescing filter positioned downstream of the moisture separator. 
     
     
       13. The gas dryer of  claim 12  further comprising at least one drain valve in fluid communication with the moisture separator and the coalescing filter. 
     
     
       14. The gas dryer of  claim 11  further comprising a regeneration blower operably connected with the secondary gas flow path. 
     
     
       15. The gas dryer of  claim 11  further comprising a regeneration gas heater positioned in the secondary gas flow path upstream of the desiccant wheel. 
     
     
       16. The gas dryer of  claim 11  further comprising a motive source operable to rotate the desiccant wheel. 
     
     
       17. The gas dryer of  claim 11 , wherein secondary gas flow path includes an outlet downstream of the desiccant wheel connected to the primary gas flow path upstream of an evaporator in the refrigerant drying circuit. 
     
     
       18. A method comprising:
 transporting a primary flow stream of pressurized working fluid discharged from a compression device through a primary flow path; 
 cooling the pressurized working fluid in a precooler heat exchanger; 
 chilling the pressurized working fluid in a refrigerant evaporator; 
 separating a first quantity of moisture from the pressurized working fluid in a moisture separator located in a refrigerant circuit downstream of the refrigerant evaporator; 
 separating a second quantity of moisture from the pressurized working fluid in a desiccant wheel downstream of the moisture separator; 
 separating the pressurized working fluid from the primary flow stream into first and second flow streams upstream of the desiccant wheel; and 
 reheating the pressurized working fluid prior to delivery to an end user. 
 
     
     
       19. The method of  claim 18 , further comprising:
 flowing the first flow stream through the desiccant wheel; 
 drying the pressurized working fluid in the first flow stream; and 
 wherein a pressure dew point temperature of the pressurized working fluid downstream of the desiccant wheel is below 32 degrees F. and actual temperature is above 32 degrees F. 
 
     
     
       20. The method of  claim 18 , further comprising:
 flowing the second flow stream through the desiccant wheel; 
 regenerating the desiccant wheel by removing moisture with the pressurized working fluid in the second flow stream; 
 merging the second flow stream with the primary flow stream upstream of the evaporator.